Aligned composite structures for mitigation of impact damage and resistance to wear in dynamic environments

Abstract

Fibrous monolith composites having architectures that provide increased flaw insensitivity, improved hardness, wear resistance and damage tolerance and methods of manufacture thereof are provided for use in dynamic environments to mitigate impact damage and increase wear resistance.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a divisional of U.S. patent application Ser. No. 10 / 310,594 filed Dec. 4, 2002, which is a continuation-in-part of U.S. patent application Ser. No. 10 / 005,084, filed Dec. 4, 2001. This application also is based on, and claims the benefit of, U.S. Provisional Application No. 60 / 251,172, filed on Dec. 4, 2000, and entitled “Aligned Fibrous Monolith Constructs for Mitigation of Foreign Object Damage in Dynamic Environments.” The specifications of these applications are incorporated herein by reference.[0002] This invention was made with U.S. Government support under grants DE-FC02-96CH10861 and DE-FC26-01NT41051 awarded by the Department of Energy. Accordingly, the Government may have certain rights in the invention described herein.FIELD OF THE INVENTION [0003] The present invention relates to fibrous monolith composites that provide increased flaw insensitivity, improved hardness, wear resistance, and damage tolerance...

AI Technical Summary

Benefits of technology

[0012] The present invention relates to structures that include unique architectural arrangements of fibrous monolith (“FM”) composites to provide the structures with enhanced mechanical properties, including increased flaw insensitivity, increased wear resistance, and damage tolerance. The present invention also relates to methods of fabricating such composites and structures.

[0013] Fibrous monoliths are a unique class of structural materials that have mechanical properties similar to continuous fiber reinforced ceramic composites (“CFCCs”). Such properties include relatively high fracture energies, damage tolerance, and graceful failures, as well as chemical inertness and thermal shock resistance. In contrast to CFCCs, however, FMs can be produced at a significantly lower cost. FMs, which include ceramics and / or other metals, generally may be manufactured by powder processing techniques using inexpensive ceramic or metal powders or combinations thereof. As a result of the high performance characteristics of FMs and the low costs of manufacture, FMs can be used in a wider range of applications than heretofore typical for monolithic ceramic composites.

[0014] The composite materials of the present invention may be used as coatings for existing structures to mitigate impact damage in dynamic environments and to reduce wear on the structures, as the composites demonstrate very high fracture energies, increased flaw insensitivity, increased wear resistance, and increased damage tolerance. The composite materials also may provide a renewable coating material having superior wear and lubricating characteristics for surfaces of ball bearings, wear parts, such as cutting tool inserts and, round tools, including drills, endmills and routers, and the like where it is desired to include a lubricating material to further reduce wear. In other aspects, a more substantial portion of, or even a complete, structure may be formed from the FM composites, thereby extending the benefits obtained with use of the FM composites.

[0015] Generally, FM composites include one or more filaments having at least a core material and a shell material, which generally are selected from diamond, graphite, ceramic oxides, ceramic carbides, ceramic nitrides, ceramic borides, ceramic silicides, ceramic phosphates, metals, metal alloys, intermetallics and combinations thereof. A plurality of filaments may be bundled together one or more times to provide a final filament that includes a plurality of core and shell phases of reduced diameters. An FM composite may include a plurality of core phases maintained in spaced separation by one or more shell phases. Such arrangements inter alia result in controlled failure of the structure to avoid unpredicted, catastrophic failures. The core phases of the FM composites, which typically provide structural strength and hardness, may include ceramic, carbide and metallic materials. The shell phase(s) typically enhances the toughness of the composite structure by creating pressure zones, microcrack zones, ductile-phase zones, and / or weak debond-type interfaces. These weak interfaces between the discrete core phases are intended to deflect cracks and to delaminate, thereby limiting brittle failure of the FM composite.

[0016] In other embodiments as referenced above, at least one of a core or shell material of the FM composite includes a lubricious composition to further reduce wear associated with high cutting and contact forces. The lubricious composition may be selected to enhance wear resistance as well as the cosmetic attributes of the composite structure. A plurality of filaments having a lubricious shell composition may be bundled together to provide a predetermined amount of the lubricating composition at the wear surface. In other aspects, a monolithic structure having a wear surface includes a lubricious composition contained within the monolithic structure to provide a predetermined amount of the lubricious composition at the wear surface at any time during the life of the structure. The structures are fabricated so that a predetermined amount of the lubricious composition is available at the wear surface even as the surface is worn down by use. The lubricious composition essentially serves as a renewable lubricating coating for the wear surface during the life of the structure.

Problems solved by technology

Such arrangements inter alia result in controlled failure of the structure to avoid unpredicted, catastrophic failures.

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